Regeneration of telegraph signals



Nov. 21, 1944. w. A. ANDERSON 2,363,278

REGENERATION OF TELEGRAPH SIGNALS Filed Jan. 11, 1943 r a,bccLe'F 9 hijklmnop T ATTORNEY Patented Nov. 21, 1944 UNITED STATE REGENERATION or TELEGRAPH SIGNALS Warren A. Anderson, New Dorp, Staten Island,

N. Y., assignor to Radio Corporation of Ameriica, a corporation of Delaware Application January-11, 1943, Serial No. 471,927

11 Claims. (01. 178-40) This invention relates to the regeneration of received telegraph signals, which at times deviate from the original form due to transmission effects of one kind or another. The changes in form are due to the subtraction oraddition of energy from or to the signals. When these occur at thestart or end of a signal-they are called bias changes. When subtractions occur Withusually been accomplished by utilizing comparatively short portions of the signal bauds, usually at the center, to. operate a polar relay, vacuum tube locking circuit'or other device to fill in the gaps between the'portions selected. These prior systems are based' on the assumption that the center of the baud is likely to be leastcaflected by the phenomena mentioned and they more or less satisfactorily reduce bias effects, butintroduce errors when splits and fills occur at the centers of the bauds.

It is an object of this invention to provide means for regenerating signals that is substantially independent of splits and fills as well as bias changes. a I

Another object of the invention is to develop a signal free fromsplits and fills, with whatever bias exists, and regenerate this developed signal into another one having neutral bias.

Another object of the invention is to convert splits and fills into bias changes and regenerate ghe converted signalto eliminate this and other Other objects of the invention will appear in the following description, reference being had to the drawing, in which:

Figure 2 isa series of graphs illustrating the theory of operation of theinvention.

Referring toFig. 1, the signal, received by de- 1 sistance- Hi to the C terminal.

the plate and the negative bias terminal 9 of the power supply 6, ground being the positive terminal of the bias source. The plate oftube l is connected through resistances l0 and. to the supply terminal 5. A thyratron or grid control gas tube l2 has its cathode connected to ground, its plate connectedbetween the resistances Ill and II and its grid connected to an intermediate pointinresistance l3, having one terminal connected to the plate of tube '1 through diode valve 14 and the other terminal connected to the C terminal. The 'poling of thediode is such that current-can fiowfrom the plate terminal of tube 1 therethrough,,but not in the reverse direction. jv Pulse-formingcondenser I5 has one terminal connected to a point between resistances I0 and lrand its other terminal connected through -re- Condenser I! hasone terminal connected to the cathode of diode l4 and the other terminal connected to ground. Thyrat'ron 18 has its plate-cathodecircuit connected across condenser I! as its sole'B supply. The gridof-this' thyratron is connected through a suitable resistance I9 to the junction pointof condenser l5 withi resistance I 6.

The second chain of control circuits is connected to the output of limiting amplifier tube 3 through a reversing amplifier tube 311, having'its input circuit connected from a point in resistance 8 to ground.. The-second chain of control circuits from the'output of amplifier 3a includes the same devices as specified in'the first chain of circuits.

. These have been'given the same reference charvices not shown, is applied as a negative-voltage across lines I and 2 connected to the grid and cathode, respectively, of limiting amplifier tube 3. The grid of thistube has a resistance connection to ground and the cathode is connected directly to ground. The plate is connected through resistance 4 to the terminal 5 of the B supply source generally indicated at 6. The output .of tube 3' is supplied to two diiTerent chains" acters as those inthe' first circuit except that the letter a has been added to distinguish therefrom.

In view of the'insertion of the amplifying tube 3a in the'circuit-,'the second chain will have potentialsfsii'nilar to the first chain butof opposite sign. v

Thyratrons' l'l and l2a" are arranged so that 'on'e commutates the other by virtue of the capacity 20 'connected across their anodes.

The commutati'ng'action ofa conde'nseron paired thryaltrons is well known, but a description of a sim ilar hook-up may be found in Patent 2,237,522 grantedto G.-R. Clark, April 8, 1941.

The anode of thyratron I2 is connected through resistance 2! and blocking condenser 22 the speed of the receiving distributor, not shown.

other terminal of the coil is connected to ground' The anode of thyratron In is similarly connected through resistance Zia, condenser 22a and coil 23a to ground. Amplifier tube 25 has its grid-cathode circuit connected to receive the drop in resistance II as a negative input potential. The plate of tube 25 is connected through resistance 26 to the plus B2 terminal 21 of the power supply device 6. The plate of tube 25 is connected to the grid of a double triode 28 through diode valve 29 and condenser 30. Resistance 3I is connected in shunt to the diode. The poling of the diode and the time constants are such that the condenser 30 can discharge suddenly therethrough but must charge only through the resistance 3| at a relatively slower rate.

Double triode 28, together with double triode 32, are connected as a Finch locking circuit with the grids of one tube connected through a resistance to the plate of the other. The operation of the Finch locking circuit is well known, but a detail description of a similar hook-up may be found in the patent of R. E, Mathes, 2,214,642, September 10, 1940.

A second chain of circuits connects the output of thyratron I2a to the grid of tube 32 through tubes 25a, 29a, condenser 30 and shunt resistance 3Ia in the same way as the first chain between thyratron I 2 and tube 28. Similar parts in the second circuit are given the same reference characters as in the first, with the letter a appended to indicate the similarity.

The grids of tubes 28 and 32 are connected through suitable resistances 33 and 34, respectively, to the plus terminal 35 in the power supply 6. The cathodes of the double triodes 28, 32 are connected to the junction point of the cathodes of tubes 25 and 25a. The plates of tubes 28 and 32 are connected together through resistance 36 and the adjustable mid-terminal 31 of this resistance is connected to the plus terminal 2'! of the power supply. The coil of polar relay 38 is connected across a portion of the load resistance 3B of the locking circuit. The stationary contacts of the relay are connected to opposite potential terminals, such as positive and negative, and the tongue is connected to the signal utilization line.

The theory of operation of the invention may now be described:

The tubes I and Ia are biased to cut oil and all four thyratrons are grid-biased below striking potential.

Suppose the signal, impressed negatively across terminals I and 2, has the form shown in graph A of Fig. 2. At time or phase a, limiter tube 3 is blocked and there is no drop in resistance 4. Tubes I and 3a therefore conduct. The conduction of tube 3a at this point blocks tube Ia. Thyratrons I811 and IM were quenched previous to this time. The blocking of tube Ia raises the potential of the plate to full value. This causes condenser Hot to charge through diode I 4a, as indicated by graph B. The grid potential of thyratron I2a will rise in value as the condenser charges and at time c the firing point of tube I2a is reached. This tube will then strike and quench thyratron I2 by the commutating action of condenser 20. At this same time the condenser Ila ceases to charge, due to the drop in resistance IIa. The quenching of thyratron I2 places full potential across the circuit containing condenser I and resistance L6 and quickly charges this condenser. This produces a pulse of voltage across resistance IS. The pulse of voltage causes thyratron I8 to strike, but it extinguishes when condenser I'I substantially instantly discharges through it. Tube I is still conducting at time c resistance I0, so condenser I'I does not start recharging at this time.

The received mark ends at time d, which unblocks tube 3 and this unblocks tube Ia and blocks tube 1. The unblocking of tube Ia at this time has no immediate effect, as thyratron I2a is still conducting and producing a drop in resistance I la. The blocking of tube puts full B1 potential on its plate and condenser II starts charging through diode I 4, as indicated by graph C. At time f, the charge in condenser II causes thyratron I2 to strike, which stops the charging of and its plate potential is low due to the drop in (IS this condenser due to the drop in resistance II. At the same time, thyratron I2a is quenched by commutating action of condenser 20, which differentiates a voltage pulse in resistance Iiia through. condenser I5a. This fires thyratron I8a, but it extinguishers at once from the loss of plate voltage by the discharge of condenser I'Ia. When time h is reached, space ends and mark starts and the action is repeated for this and subsequent signals in a way that will be evident from the description of the operation already given.

Returning now to the time c in Fig. 2, when thyratron I 2a fires and thyratron I2 quenches, the drop in resistance Ila is'applied in a negativedirection in the grid circuit of amplifier 25a. which blocks it. Simultaneously, the removal of the drop in resistance I I unblocks amplifier tube 25. This action does not disturb the balance of the locking circuit, as the variation in plate current flow in the plate circuit of tubes 25 and 25a is too slight. At time e, a tooth in tone Wheel 24 passes under the magnet passing through coils 23 and 23a, which suddenly reduces the reluctance of the magnetic circuit. Pulses are produced in both coils, but that in coil 23a is not effective due to the blocking of tube 25a. The pulse in coil 23 passes through blocking condenser 22, 'resistance 2I and resistance Ii to the plus B terminal of the power supply, thence to ground and back to the coil. This pulse is shown at 39 in graph E. It will be noted that this pulse is applied as a positive voltage in the grid circuit of the tube and this produces a dip or inverse pulse in the plate potential of this tube. When this momentary decrease of plate potential occurs, condenser 30 discharges through diode 29, the plate-cathode circuit of tube 25 to ground and back through resistance 33 to the condenser. The drop produced in resistance 33 makes the grid more negative or less positive and this reduces the anode current in locking tube 23, which raises the potential on the grid of tube 32, due to the cross connection of the plate and grid circuits. The cumulative action blocks tube 23 and unblocks tube 32, the later having previously been blocked. This is the-action of the well-known Finch locking circuit. Condenser 36 immediately starts recharging through resistance 3|, but the current is notsufiicient to throw the locking circuit, due to the time constant of this charging circuti.

When the locking circuit is thrown, as described, the upper terminal of the coil of relay 38, as shown in Fig. 1, becomes positive in respect to the lower terminal and the switch tongue is moved, say, against the positive terminal and the mark starts at point e, as shown in graph F. This mark will continue until the locking circuit is thrown in the opposite direction. This occurs at point g, when thyratron I2 is conducting and thyratron I2a is non-conducting, and a tooth on the tone wheel is passing under the magnet inside coils 23 and 23a. The pulse produced in coil 23a of the tone 'wheel'will be effectivefsince at such time amplifier 25ais unblocked and char throughdiode 29a, the plate-cathode circuit of tube 25d andresistance-33. This action generation of the first mark. It will be noted that mark in this regenerated signal is a negative voltage, but it may be, if desired, made positive by reversing the potentials at the terminals of relay 38. The succeeding space will continue up to the point e, where the locking circuit will bethrown in the opposite direction in the way already described in connection with pulse 39.

Since the tone wheel is'connected to the receiving distributor, which is maintained at a speed proportional to the distributor, at the trans-.

mitter, the marks and spaces in graph F are correctly formed. Graph D, as will be seen, is the regenerated signal free from the effects of splits and fills, but with Whatever received bias it may contain. If a'split should occur between times a and c, the only effect would be a slight reduction of the charge of the condenser Ila, which would slightly change the firing time of thyratron PM, but it would not prevent the starting or ending of the mark as in the prior art systems. It would merely delay it slightly. The regenerated signal at-D has an energy content proportional to that of the received-signal, but the change of energy due to a split or fill is converted into a bias change. This has nodeleterious effect since bias is eliminated in the regenerated signal of graph F. It should be noted, however, that graph D, as shown, does not show a bias change, as that graph assumes the absence of splits and fills.

While I have shown triodes in the drawing, this has been by way of example and, of course, pentodes or other forms of tubes may be used. Also, other forms of electric valves may be used in place of the diodes, if desired.

Instead of using a tone wheel generator to produce pulses in correct phase relation, Iinay employ the electronic system for producing these pulses, disclosed in the joint application of Alfred Kahn and myself, filed November 19, 1942, Serial No. 466,094, as well as any other pulse-forming system. Various other modifications may be used without departing from the spirit of the invention.

' mutilations in their intermediate portions, which comprises producing a second signal having marksand spaces free from said mutilations and with energy content proportional to that of the marks and spaces .of the received signal, producing a series of pulses in constant phase relation with the signal bauds at the transmitter and producing a third signal by'the combined effect of the voltage of said pulses and the voltages of the marks and'spac'es of the second signal occurring simultaneously therewith.

2. The method of regenerating a received telegraph signal having marks and spaces with mutilations in their intermediate portions, which comprises producing a second signal having marks and spaces free from said mutilations and with energy content proportional to that of the marksand spaces of the 'receivedsignal, producing a series of pulses in constant phase relation with the signal bauds at the transmitter, combining the voltage of said pulses and the voltages of the marks and spaces'of the second signal occurring simultaneously therewith and producing a third signal by said combined voltages. I

3. The method of regenerating a received telegraph signal having marks and spaces with mutilations in their intermediate portions, which comprises producing a second signal having marks and spaces free from said mutilations and with energy content proportional to that of the marks and spaces of the received signal, producing a series of voltage pulses in constant phase relation with the signal bauds at the transmiter, combining the voltages of said pulses and the voltage of the marks and spaces of the second signal occurring simultaneously therewithwith, and starting the marks of a third signal by'the combined voltages in the first bauds of the second signal marks and ending the marks by the combined voltages in the first bauds of the'succeeding spaces.

4. The method of regenerating a received tele-' graph signal having marks and spaces with splits and fills andhaving energy content proportional 0 to tha't ofthe marks and spaces of the received signal, producing pulses in constant phase relation with the signal bauds at the transmitter, combining the voltages of the pulses with the voltages of selected middle portions of the bauds of the second signal and starting a third signal with the combined voltage in the first bauds of the marks of the second signal and ending the marks with the combined voltage in the first bauds of the succeeding spaces.

5. The method of regenerating a received telegraph signal having marks and spaces with splits and fills, which comprises producing a second signal having marks and spaces with bias changes equivalent to said splits and fills, producing pulses in constant phase relation'with the signal bauds at the transmitter, combining the voltages of the pulses with the voltages of selected middle portions of the bauds of the second signal and starting'a third signal with the combined voltage in the first bauds of the marks of the second signal and ending the marks with the combined voltage in the first bauds of the succeeding spaces.

6. In apparatus for regenerating a received telegraph signal having marks and spaces containing splits and fills, means for producing marks and spacesof a second signal without the splits and fills and having energy content proportional to that of the received signal, means for producing a series of pulses'in constant phase relation with the signal bauds at the transmitter, means for combining the voltage of the pulses with the voltage of the middle portion-of;

the bauds of said second signal and means/for starting marks of a third signal with the comand for ending them with the combined voltage in the first bauds of the succeeding spaces.

7. In apparatus for regenerating a received telegraph signal having marks and spaces containing splits and fills, means for producing marks and spaces of a second signal with bias changes equivalent to said splits and fills, means for producing a series of pulses in constant phase relation with the signal bauds at the transmitter, means for combining the voltage of the pulses with the voltage of the middle portion of the bauds of said second signal and means for starting marks of a third signal with the combined voltages in the first bauds of the marks and for ending them with the combined voltage in the first bauds of the succeeding spaces.

8. In apparatus for regenerating received telegraph signals having splits and fills in the mark and space bauds, a pair of energy storing devices, means for starting the storing of energy in one of said devices at,the start of the marks and for terminating said storing at predetermined subsequent points in said first bauds, means for starting the storing of energy in the other of said devices at the end of the last bauds of the marks and for terminating said storing at predetermined subsequent points in the first bauds of the succeeding spaces, means controlled by a predetermined state of storage of the first device for starting the marks of a second signal,

means controlled by a predetermined state of storage of the second device for ending said marks, means for producing a series of pulses in constant phase relation with the signal bauds at the transmitter, means for combining the voltage of the pulses with the voltage of the middle portion of the bauds of said second Sig: nal and means for starting the marks of a third signal with the combined voltages in the first bauds of the marks of the second signal and for starting the succeeding spaces with the combined voltages in the first bauds of the succeeding spaces thereof. 7

9. In apparatus for regenerating received telegraph signals, a pair of condensers, means for starting the charging of one condenser at the start of the first bauds of the marks and for 'graph signal having terminating said charging at predetermined subsequent points in said first bauds, means for starting the charging of the second condenser at the end of the last bauds of the marks and for terminating said charging at predetermined subsequent points in the first bauds of the succeeding spaces, means controlled by a predetermined voltage of the first condenser for starting the marks of a second signal, means controlled by a predetermined voltage of the second condenser for starting the succeeding spaces, means for producing a series of pulses in constant phase relation with the signal bauds at the transmitter, means for combining the voltage of the pulses with the voltage of the middle portions of the bauds of said second signal and means for starting the marks of a third signal with the combined voltages in the first bauds of the marks of the second signal and for starting the succeeding spaces with the combined voltages in the first bauds of the succeeding spaces thereof.

10. The method of regenerating a received telemarks and spaces with mutilations in their intermediate portions, which comprises producing a series of pulses at constant phase points of the signal bauds at the transmitter, eliminating any mutilations of the signal at the same phase points of the received signals, combining the voltages of said pulses and the voltages of the. received marks and spaces at said phase points and producing a re generated signal by said combined voltages.

11. The method of regenerating a received telegraph signal having marks and spaces with mutilations in their intermediate portions, which comprises transferring the mutilations to the ends of the marks and spaces to produce a signal free of said mutilations but with bias equivalent thereto, producing a series of pulses in constant phase relation-with the signal bauds at the transmitter and producing a third signal by the combined effect of the voltage of said pulses and the voltages of the marks and spaces of the second signal occurring simultaneously therewith.

WARREN A. ANDERSON. 

